New lints: functions with explicit ABI export names about cargo-semver-checks HOT 2 OPEN

Hi! I started to work on this. A couple of questions/uncertainties:

1. I'm assuming it's a major-level change based on other violations like changing an established repr, although I couldn't find anything on the cargo semver page. for no_mangle/export_name specifically
2. Is it a violation when a non-public function changes export name? For example, in the example you linked, you can still access im_secretly_public even when it's not public in the Rust API.
3. Should this (these) lints proc when the export name of one function moves to a different function? For example,

#[no_mangle]
pub fn func1() {}

pub fn func2() {}

to

pub fn func1() {}

#[export_name = "func1"]
pub fn func2() {}

Thanks!

from cargo-semver-checks.

Great questions!

I'm assuming it's a major-level change based on other violations like changing an established repr, although I couldn't find anything on the cargo semver page. for no_mangle/export_name specifically

Yes, it's a major breaking change. The cargo semver reference isn't yet an exhaustive list of major changes, and we've had many situations where cargo-semver-checks work triggered additions to the reference or vice versa. I expect that trend will continue for some time :)

Is it a violation when a non-public function changes export name? For example, in the example you linked, you can still access im_secretly_public even when it's not public in the Rust API.

Yes! I believe we might actually have a lint for this already. It seems familiar and may have been added sometime in the last couple of months.

Should this (these) lints proc when the export name of one function moves to a different function? For example,

Great edge case! No, this should not trigger either lint.

In general, we want to trigger lints when we are certain there's a problem, so that we skew heavily away from false-positives which cause users to distrust the tool. In this edge case, the change may have been intentional and from an API/ABI perspective seems fine.

However, if the func2() function e.g. takes a different number of arguments, then that should trigger a lint — I'm adding that plus related cases to the list.

from cargo-semver-checks.